Magnetic head slider and a magnetic disk device in which the slider is mounted

ABSTRACT

A magnetic head slider having a magnetic head for reading/writing information from/into a magnetic disk and a slider on which the magnetic head is mounted. The slider has three surface portions with levels which are different from each other on a surface facing to the magnetic disk including a first surface portion forming a pad surface, a second surface portion having a level which is lower than a level of the first surface portion and a third surface portion having a level which is lower than that of the second surface portion. The second surface portion is provided at a side opposite to a side on which the magnetic head is mounted and the third surface portion is provided at the side on which the magnetic head is mounted. A projection is provided on the second surface portion.

CROSS REFERENCE TO RELATED APPLICATION

This is a continuation of U.S. application Ser. No. 09/299,909, filedApr. 28, 1999, U.S. Pat. No. 6,373,661 B1 the subject matter of which isincorporated by reference herein.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a magnetic head slider for a magneticdisk device and also to a magnetic disk device, and more particularly toa magnetic head slider of a low flying height-type for achieving highreliability and high-density recording and also to a magnetic diskdevice having such a magnetic head slider.

2. Description of the Related Art

In magnetic disk devices, attempts have now been made to achieve a lowflying height design of a slider and also to stabilize a flying height

For example, as disclosed in JP-A-6-325530, there has been proposed aslider in which a surface (step surface) structured by a step extendingin a recessing direction from a flat surface portion of a rail forflying (air bearing rail) is formed at an inflow-side portion of therail of the slider, and the depth of this step surface (that is, theheight of the step) is made microscopic so that a predetermined flyingheight of the slider can be achieved without depending on the peripheralspeed of a disk. In this known example, the rail for flying has the stepsurface provided at the inflow-side portion, the step, and the flatsurface portion extending from this step portion, and the depth of thestep surface (that is, the height difference between the step surfaceand the flat surface portion) is not more than 700 nm, and by doing so,there can be provided the slider which can fly with a predeterminedflying height without depending on the peripheral speed of the disk. Aslider, having a step of such a microscopic depth (height), will behereinafter referred to as “microscopic step slider”.

JP-A-7-21717 discloses a slider in which two inflow pads and one outflowpad are provided on the slider, and side edges of the pads are inclinedto an angle generally equal to a predicted maximum inclination so thateven on a smooth magnetic disk, the slider can be disposed in linearcontact with the magnetic disk, thereby preventing the sticking of theslider to the disk.

Further, in order to achieve the above-mentioned low flying heightdesign of the slider, the disk surface is made flat and smooth. The meansurface roughness Ra of a currently-used disk is reduced to not morethan 10 nm. There has been adopted a contact start stop system(hereinafter referred to as “CSS system”) in which when the rotation ofa magnetic disk is stopped, a slider is held in contact with a disksurface, and when the disk is rotated, the slider flies off the disksurface. In a device using this CSS system, a so-called sticking problemarises from a smooth disk surface, and more specifically, when therotation of the disk is stopped, the slider sticks to the disk surface.When the slider sticks to the disk, there are encountered troubles suchas the failure of the disk to rotate. In order to solve this problem, aslider, in which microscopic projections are formed on the slider toreduce the area of contact between the slider and the disk, is disclosedin JP-A-4-28070 and JP-A-9-245451.

In a microscopic step slider as disclosed in the above JP-A-6-325530, asticking problems arises from a smooth disk surface. In order to avoidthis sticking problem, even if microscopic projections as disclosed inJP-A-4-28070 and JP-A-9-245451 are provided on a rear portion or frontand rear portions of the flying rail, or a negative-pressure pocketthereof, the following problems are encountered:

(1) If the flying rail of the slider or the microscopic projection isbrought into contact with the disk surface for some reason at the timeof CSS or during the flying of the slider over the rotating disk, theflying surface (surface facing the disk) of the slider is pulled by africtional force, so that the slider is turned or angularly moved abouta pivot (load-acting point) of a suspension to lean forward, and as aresult the front edge of the step surface of the slider is brought intocontact with the disk surface. The front edge of the step surface issharp, and when this front edge is brought into contact with the disksurface, there arises a problem that the disk is damaged by this frontedge. Particularly in a magnetic disk device of the type in which theflying height of the slider is small, and the smooth disk is used forthe purpose of achieving a low flying height, this problem is seriousbecause of the large frictional force. Therefore, to prevent the sliderfrom leaning forward so that the front edge will not brought intocontact with the disk surface is an important subject matter forpreventing damage to the disk and for securing the reliability,

One method of overcoming this problem is to chamfer the front edge ofthe step surface (to provide a curvature) to increase the contact area,thereby reducing a contact stress (load pressure). With this method,however, an opening of the step surface (that is, the distance of thestep surface from the disk surface) is large, and an increased amount ofdust and dirt enter this opening, which leads to a possibility that theflying height is varied. When the flying height is thus varied, an errorin the data reading and writing operation occurs. Therefore, this methodis not effective in preventing the damage of the disk by the front edge(sharp edge portion) of the step surface.

(2) Another main factor in the variation of the flying height of theslider is a reduction of the atmosphere pressure. More specifically,when the magnetic disk device is used at a place of a high altitude, thepressure of the atmosphere is low, so that the flying height is reduced.When the flying height is reduced, there arises a problem that theslider comes into contact with the disk to damage the same. To reducethe amount of reduction of the flying height of the slider due to thedecrease of the atmospheric pressure is an important subject matter forachieving the low flying height design of the slider and also forpreventing the contact of the slider with the disk so as to secure thereliability.

And besides, when the microscopic projection is provided on the rail ofthe slider, the reduction of the flying height is, in some cases,limited depending on the height of this projection, so that there is acase that the low flying height design can not be achieved.

OBJECT AND SUMMARY OF THE INVENTION

It is therefore an object of the present invention to provide a magnetichead slider in which even when the slider is leaned forward, a frontedge of each step surface is prevented from being brought into contactwith a disk surface, and besides the amount of reduction of the flyingheight of the slider due to a decrease of the atmospheric pressure isreduced, thereby enabling the reading and writing of data in a stablemanner, and to provide a magnetic disk device of a high reliability.

In order to achieve the above object, and in order to prevent a stepslider from leaning forward and a front edge of each step surface fromcoming into contact with the disk surface, rails for flying (steppedpads) each structured to have a step surface are provided on a slider,and microscopic projections are formed on the step surface disposed atan inflow-side portion of the slider. The height of the microscopicprojections are substantially equal to or higher than the depth (height)of the step. And besides, because of the provision of the microscopicprojections, a variation of the flying height due to the decrease of theatmospheric pressure can be reduced.

The microscopic projections are formed on the step surface of the railof the slider of the invention. The front edge of the step surface isprovided at a position substantially coincides with the inflow end ofthe slider.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of a first embodiment of a slider of theinvention, showing a flying surface thereof;

FIG. 2 is a view explanatory of the condition for the forward leaning ofthe slider by a frictional force;

FIG. 3 is a view explanatory of the function of microscopic projections;

FIG. 4 is a diagram showing the relation between the depth of a stepsurface and a flying force;

FIG. 5 is a view showing a pressure distribution of the slider;

FIG. 6 is an enlarged view of a portion A of FIG. 2;

FIG. 7 is a perspective view of a second embodiment of a slider of theinvention, showing a flying surface thereof;

FIG. 8 is a front view of the second embodiment of the slider;

FIG. 9 is a perspective view of a third embodiment of a slider of theinvention, showing a flying surface thereof;

FIG. 10 is a perspective view of a fourth embodiment of a slider of theinvention, showing a flying surface thereof;

FIG. 11 is a perspective view of a fifth embodiment of a slider of theinvention, showing a flying surface thereof;

FIG. 12 is a perspective view of a sixth embodiment of a slider of theinvention, showing a flying surface thereof;

FIGS. 13A-13E is a view showing a method of forming a pad for flying;and

FIG. 14 is a perspective view of a magnetic disk device incorporating amagnetic head slider of the invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

A first embodiment of the present invention will now be described withreference to FIGS. 1 to 6 and FIG. 14.

FIG. 1 is a perspective view of one embodiment of a slider of theinvention, showing a flying surface thereof.

Three pads for flying 10 for producing a flying force are formed on ableed surface 11 of the slider 1. Two of these pads 10 are providedrespectively at opposite ends of an inflow-side portion (to which an airstream, produced in accordance with the rotation of a disk, flows) ofthe slider 1, and the other pad 10 is provided at a central portion of aan outflow-side portion of the slider 1. Each flying pad 10 has a flatsurface portion 13, a step portion 14 (defined by a surface disposedgenerally perpendicular to the flat surface portion 13) facing the airstream inflow side, and a step surface 12. The flat surface portions 13of the three flying pads 10 lie generally in a common horizontal plane.The step surface 12 is disposed generally parallel to the flat surfaceportion 13, and structured to have a microscopic depth (the step portion14) in a direction generally perpendicular to the flat surface portion13. The step surfaces 12 of the three flying pads 10 lie generally in acommon horizontal plane. A microscopic projection 17 is formed on thestep surface 12 of each of the two inflow-side pads 10. The microscopicprojection 17 is disposed near an outer corner portion 16 a of the stepsurface 12. The slider 1 is provided with a thin-film magnetic head 20provided rearward of the flat surface portion 13 of the outflow-side pad10. A gap portion 21 of the magnetic head 20 is disposed generally in aplane in which the flat surface portion 13 lies. A coil portion 22 andlead terminals 23 are provided at the outflow end surface of the slider1.

In this embodiment, the flying pads each having the step are used inorder to achieve the same effect as attained with the conventionalflying rail having an inclined portion at the air inflow side. Namely,the flying pads each with the step are used in order to obtain a largeflying force.

One example of specific numerical values in this embodiment are asfollows. The slider 1 has a length of 1.2 mm, a width of 1 mm and athickness of 0.3 mm. The size of each of the step surface 12 and theflat surface portion 13 of the flying pad 10 is 0.4 mm×0.1 mm, and theheight of the step portion 14 is 0.09 μm. The height from the flatsurface portion 13 to the slider surface (that is, the depth (height) ofthe bleed 11) is 6 μm. The microscopic projection 17 has a cylindricalshape, and its diameter is 0.06 mm, and the height of this projection 17from the step surface 12 is 0.13 μm. Therefore, the microscopicprojection 17 projects 0.04 μm beyond the flat surface portion 13. Theslider 1 is not limited to the above dimensions, and there is a tendencyfor these dimensions to become more microscopic.

Effects of the present invention will now be described with reference toFIGS. 2 and 3. FIG. 2 is a side view of the magnetic head slider of thepresent invention. FIG. 3 shows the slider with the microscopicprojections and the slider without the microscopic projections, showinga contact condition between the slider and a magnetic disk.

If the slider is brought into contact with a rotating magnetic disk 70for some reason during the flying of the slider 1 or at the time of CSS,a force as shown in FIG. 2 is exerted at a point of contact between theslider land the magnetic disk 70. Although not shown in the drawings, apressing force, acting in a direction toward the magnetic disk, isexerted on the slider 1 from a pivot of a suspension. When a moment Mfdue to a frictional force F between the slider 1 and the magnetic disk70 becomes larger than a turning moment Mw due to the pressing loadapplied to the slider 1 by the suspension, the slider 1 is turned aboutthe pivot to lean forward, so that the front edges of the step surfacesare brought into contact with the disk surface.

The condition for the forward leaning of the slider 1 is Mw<Mf. Here,there are established formulas, Mw=W×l and Mf=F×d where W represents thepressing force applied to the slider by the suspension, l represents thedistance from the pivot (load acting point) to the point of contact(axis of the turning movement) between the slider 1 and the magneticdisk 70, F represents the frictional force between the slider 1 and themagnetic disk 70, and d represents the thickness of the slider 1.

As will be appreciated from the above formulas, in order to prevent theforward leaning of the slider, it is effective to increase the pressingload W, or to increase the distance l from the pivot to the point ofcontact between the slider and the disk, or to reduce the thickness d ofthe slider. However, the increase of W increases the amount of wearbetween the slider and the disk at the time of CSS, and this is notdesirable. For reducing the thickness d of the slider 1, the size of themagnetic head also need to be reduced, and this is difficult. Therefore,it is effective to increase the value of l.

If the microscopic projection 17 is formed on the step surface of eachof the flying pads provided at the inflow-side portion of the slider asshown in FIG. 2, Mw increases so that the slider 1 is less liable to beturned to lean forward. More specifically, assuming that the overalllength of the slider is represented by L, the length of the step surfaceis represented by ls, the pivot is disposed generally at the center ofthe slider, and the microscopic projection 17 is provided at the centerof the step surface, the following is obtained:

If the turning moment of the conventional microscopic step slider isrepresented by Mw1, the following formula is established:

Mw 1=W×(L/2ls)  (1)

If the turning moment of the microscopic step slider of the presentinvention is represented by Mw2, the following formula is established:

Mw 2=W×(L/2)  (2)

In the present invention, the microscopic projection 17 is provided oneach step surface 12 at the inflow side. Therefore, the axis of turning(angular movement) of the forwardly-leaning slider 1 is the point ofcontact between each microscopic projection 17 and the magnetic disk 70.The condition for the turning of the slider 1 is represented by formula(2) as described above. On the other hand, the conventional slider hasno microscopic projection 17, and therefore the boundary between thestep surface 12 and the flat surface portion 13, that is, the inflow endof the flat surface portion 13, serves as the axis of turning of theslider (that is, the point of contact with the magnetic disk).Therefore, the value of l is reduced by an amount corresponding to thelength is of the step surface 12, so that the slider is liable to leanforward. In other words, if the microscopic projection 17 is formed onthe step surface 12 as in the present invention, the value of l isincreased, so that the slider 1 is less liable to lean forward.

As will be appreciated from the above formulas, by providing themicroscopic projection on the step surface of each inflow-side pad, themoment can be increased, so that the slider is less liable to leanforward.

In the present invention, there is achieved an advantage (effect) thateven when the slider leans forward, the slider is less liable to damagethe surface of the magnetic disk. If any microscopic projection 17 isnot formed on the step surface 12 as shown in FIG. 3(1), the slider isliable to be leaned forward by the frictional force F as describedabove. When the slider thus leans forward, the front edge 16 of the stepsurface 12 is brought into contact with the surface of the magnetic disk70 to damage the same. In order to prevent the intrusion of dust anddirt and also to reduce the depth Ds of the step surface 12, the frontedge 16 of the step surface 12 is formed into a sharp edge. Therefore,when the slider 1 is brought into contact with the surface of themagnetic disk, a contact stress can easily exceed a stress limit of themagnetic disk surface, thereby damaging the magnetic disk. If themagnetic disk is thus damaged, an error in the information reading andwriting operation occurs, thus adversely affecting the reliability ofthe device.

On the other hand, in the case where the microscopic projection 17 isformed on the step surface of each inflow-side pad, the microscopicprojection 17 is brought into contact with the magnetic disk 70 when theslider 1 leans forward as shown in FIG. 3(2), and the front edge 16 ofthe step surface 12 will not be brought into contact with the surface ofthe magnetic disk 70. The contact area of the microscopic projection 17is so small that the microscopic projection 17 hardly damages themagnetic disk surface. As shown in the drawings, the height of themicroscopic projection 17 need only to be so determined that the cornerportion of the flat surface portion 13 will not be brought into contactwith the disk surface, and this height may be smaller than the height ofthe flat surface portion 13.

When the slider without any microscopic projection is leaned forwardwhile turned in the direction of the width (transverse direction), thecorner portion 16 a of the front edge 16 of the step surface 12 isbrought into contact with the disk surface. The contact of the cornerportion 16 a with the disk surface is more liable to damage the disksurface than the contact of the front edge 16 with the disk surface is.On the other hand, in the case where the microscopic projection 17 isformed on the outer end portion of the step surface 12, the microscopicprojection 17 is brought into contact with the surface of the magneticdisk 70, and the corner portion 16 a will not be brought into contactwith the surface of the magnetic disk 70. Therefore, in the presentinvention, even when the slider 1 is leaned forward upon contact withthe magnetic disk 70, damage to the magnetic disk 70 can be prevented.

The relation between the depth Ds of the step surface (which is theheight difference between the flat surface portion 13 and the stepsurface 12) and the flying force Q was obtained by calculation, andresults thereof are shown in FIG. 4. With respect to conditions of thecalculation, the length of the slider was 1.25 mm, its width was 1.0 mm,the size of the step surface 12 of the flying pad was 0.3 mm×0.25 mm,the size of the flat surface portion 13 was 0.3 mm×0.05 mm, and theheight from the flat surface portion to the bleed 11 was 6 μm. Theflying height of the air inflow end of the slider was 30 nm, and theflying height of the air outflow end thereof was 90 nm, and the heightDs of the step portion was used as a parameter, and the calculation wasmade.

As will be appreciated from FIG. 4, the smaller Ds becomes, the smallerthe difference between the flying force at the disk speed of 6 m/s andthe flying force at the disk speed of 12 m/s becomes. As Ds decreasesfrom 0.3 μm to 0.2 μm, the difference of the flying force due to thedifference of the speed abruptly decreases. When Ds becomes not morethan 0.2 μm, the difference of the flying force Q becomes not more than10%. This value is sufficiently smaller as compared with a variation ofthe flying force Q due to processing and assembling errors and so on.Therefore, if Ds is not more than 0.2 μm, the stable flying can beachieved. In this embodiment, the value of Ds is 0.2 μm, and thereforethere can be obtained the slider in which the predetermined flying forceQ is obtained without depending on the peripheral speed of the disk, anda variation in the flying height is small, and the flying height isconstant over the entire circumference of the disk.

This effect is not changed even if the depth of the bleed (the heightfrom the slider surface to the flat surface portion 13 of the pad)relative to the flying pad is changed. The smaller the depth Ds of thestep portion 14 is made than 0.2 μm, the smaller the difference of theflying force due to the difference of the peripheral speed becomes. Withthe compact design of the slider, the flying force Q tends to be small.However, if the height Ds of the step portion 14 is 0, this pad has nostep, so that the flying force is not produced. Therefore, in view ofvariations in the processing of the slider, the minimum value of Dsshould be so determined that it will not become 0.

FIG. 5 shows a pressure distribution on the flying surface of the sliderwith the microscopic projections, which pressure distribution wasobtained by calculation.

By providing the microscopic projection 17 on the step surface 12, theamount of reduction of the flying height can be reduced even if theambient atmospheric pressure decreases. More specifically, in the casewhere the magnetic disk device is used at a place with an altitude of3,000 m, the ambient atmospheric pressure is smaller than the ordinaryatmospheric pressure (1 atmospheric pressure), so that the flying heightof the slider is reduced. Therefore, conventional sliders need to have aseparate negative pressure-producing mechanism in order to prevent thereduction of the flying height. In the slider of the present invention,having the microscopic projection 17 formed on the step surface 12 ofeach inflow-side pad, a negative pressure-producing region is formedrearward of each microscopic projection 17, as shown in FIG. 5.Therefore, any separate negative pressure-producing portion as in theconventional sliders is not needed. Therefore, the amount of reductionof the flying height due to the altitude difference (between 0 m and3,000 m) can be made smaller as compared with the sliders having nomicroscopic projection 17.

It has been confirmed through calculation that the amount of reductionof the flying height in the construction of this embodiment is not morethan about ½ of that obtained in the slider having no microscopicprojection 17.

Although explanation of the detailed mechanism is omitted here, thefollowing relation is established among the flying height Fs of theslider, the load Wand the negative pressure Fn. The slider flies withthe flying height satisfying this relation.

Fs=W+Fn  (3)

In this embodiment, as the atmospheric pressure decreases, the flyingforce Fs decreases as in the conventional sliders, and at the same timethe negative pressure Fn decreases. Therefore, the flying height of theslider will not be changed in accordance with the decrease of theatmospheric pressure. This effect is achieved by forming the microscopicprojection on the step surface of a microscopic depth (height) asdescribed above. And besides, there is achieved an advantage that avariation of the flying force due to a change in the peripheral speed ofthe disk can be reduced as in the conventional slider utilizing anegative pressure.

FIG. 6 shows a portion A of FIG. 2 on an enlarged scale. In FIG. 6,however, the microscopic projection 17 projects beyond the flat surfaceportion 13 of each inflow-side pad. As shown in FIG. 6, the microscopicprojection 17 is formed on the step surface 12, and the height Dp of themicroscopic projection 17 is higher than the height Ds (the depth Dsfrom the flat surface portion 13 to the step surface 12) from the stepsurface 12 to the flat surface portion 13, and therefore the microscopicprojection 17 is held in contact with the surface of the magnetic disk70. Therefore, the flat surface portion 13 of each flying pad 10, havingthe microscopic projection 17, is held out of contact with the magneticdisk 70. The area of contact between the flat surface portion 13 and themagnetic disk 70 can be arbitrarily changed by adjusting the height Dpof the microscopic projection 17.

In this embodiment, the microscopic projection 17 is higher than theflat surface portion 13, and therefore the flat surface portion 13 ofeach air inflow-side flying pad 10 will not be brought into contact withthe surface of the magnetic disk 70. The flying pad 10, provided at theair outflow-side of the slider, does not come into contact with themagnetic disk 70 at its flat surface portion 13 over the entire areathereof, but come into contact with the magnetic disk at its flatsurface portion 13 at a predetermined inclination angle. Therefore, thearea of contact between the slider 1 and the disk 70 is greatly reduced.It is known that a sticking force, by which the slider sticks to thedisk, is proportional to the area of contact between the two. In thisembodiment, the area of contact is further reduced by the provision ofthe microscopic projections 17, the sticking force is reduced.

Next, the dimensions of the various portions in this embodiment will bedescribed. As described above, the depth (height) Ds from the flatsurface portion 13 to the step surface 12 is set to 0.09 μm. Therelation between this depth and the flying force will be describedlater. The depth Db from the flat surface portion 13 of the flying pad10 to the bleed surface 11 is 6 μm. For the purpose of reducing theprocessing amount, the bleed depth Db is made as small as possible insuch a range that the bleed surface will not produce a flying force, butthe value of Db is not limited to 6 μm. The height Dp of the microscopicprojection 17 is larger than Ds, and therefore Dp>0.09 μm is provided.

The diameter of the microscopic projection 17 is 0.06 mm. If thisdiameter is too small (for example, not more than 0.01 mm), themicroscopic projection 17 is worn upon contact with the magnetic disk.In contrast, if this diameter is too larger (for example, not less than0.1 mm), the microscopic projection 17 sticks to the magnetic disk. Wearand the sticking vary depending on the surface roughness of the magneticdisk surface.

In this embodiment, the amount of projecting of the microscopicprojection 17 beyond the flat surface portion 13 toward the magneticdisk surface is 40 nm (Dp−Ds=0.13 μm−0.09 μm). The height Dp of themicroscopic projection 17 is so determined that the projecting amount(Dp−Ds) is smaller than the flying height of the flat surface portion13, and is larger than the roughness of the magnetic disk surface. Ifthe mean surface roughness Ra of the magnetic disk surface is 2 nm, themaximum surface roughness Rmax is 6 nm which is about three times largerthan Ra, and therefore the projecting amount should be not less than 6nm.

The slider is inclined, and therefore with respect to the flying heightho of the air outflow-side flying pad and the flying height hi of eachair inflow-side pad, the gap ratio (hi/ho) is usually 2 to 8. In thisembodiment, hi/ho=3 is provided, and ho=20 nm and hi=60 nm are provided.Therefore, even though the projecting amount is 40 nm, the microscopicprojection will not come into contact with the rotating magnetic disk.

For the above reasons, if the flying height is made microscopic, theprojection height Dp need to be reduced so as to avoid the contact ofthe microscopic projection with the magnetic disk. Also, the projectingamount (Dp−Ds) need only to be larger than the maximum surface roughnessRmax (=3Ra), and therefore Dp may be reduced if Rmax is small.

As described above, the microscopic projection 17 is formed on the stepsurface 12 of each inflow-side flying pad, and therefore the forwardleaning of the slider is prevented, and besides even if the slider isleaned forward, damage to the disk is prevented. Furthermore, thereduction of the flying height due to the decrease of the ambientpressure is prevented, and also the sticking force is reduced.

A second embodiment of the present invention will be described withreference to FIGS. 7 and 8. FIG. 7 is a perspective view of the secondembodiment of a slider of the invention, showing a flying surfacethereof. FIG. 8 is a plan view showing the flying surface of the sliderof FIG. 7.

This embodiment differs from the first embodiment in that twoinflow-side flying pads 10 are offset inwardly from opposite sides ofthe slider 1, respectively. As shown in FIG. 8, a front edge 16 of astep surface 12 of each inflow-side pad 10 is offset slightly rearwardof a front edge 15 of the body of the slider 1. The outer side edge ofeach inflow-side flying pad 10 is offset inwardly from the correspondingside edge of the slider 1. With this arrangement, even if chippingoccurs when sliders are cut one by one from a rectangular bar bymachining, the configuration of the flying pads will not be changed bythis chipping. Therefore, the efficiency of the production by machiningcan be enhanced. Similar effects as described above for the firstembodiment are achieved also in this embodiment.

A third embodiment of the present invention will be described withreference to FIG. 9. FIG. 9 is a perspective view of the thirdembodiment of a slider of the invention, showing a flying surfacethereof.

This embodiment differs from the first embodiment in that a rear stepsurface 18 is formed at a rear side of each of two inflow-side flyingpads 10. The rear step surfaces 18 are disposed in a plane in which stepsurfaces 12 lie, that is, the rear step surfaces 18 and the stepsurfaces 12 have the same height, and are provided along outer sides 13a of the pads. Because of the provision of the rear step surface 18, anair stream, flowing to a rear side of a flat surface portion 13, islimited, and that region, disposed at the rear side of the flat surfaceportion 13, forms a negative pressure-producing region 18 a forproducing a negative pressure. The negative pressure decreases with thedecrease of the ambient pressure, and therefore even when the ambientpressure decreases, the amount of reduction of the flying height of theslider is small similarly with the effect of the negative pressure dueto the microscopic projection 17. And besides, the amount of reductionof the flying height due to the decrease of the pressure is small whenthe negative pressure is large. Therefore, a variation of the flyingheight due to the decrease of the ambient pressure is smaller ascompared with the first embodiment, and therefore there can be providedthe slider of a higher reliability. And besides, similar effects asdescribed above for the first embodiment can be expected.

A fourth embodiment of the present invention will be described withreference to FIG. 10. FIG. 10 is a perspective view of the fourthembodiment of a slider of the invention, showing a flying surfacethereof.

This embodiment differs from the third embodiment in that step surfaces12 of two inflow-side flying pads 10 are interconnected by a centralstep surface 19. Because of the provision of the central step surface19, an air stream, flowing through a gap between the two flying pads, islimited, and a negative pressure is produced at a wide region disposedat the rear side of the flying pads. The depth from a flat surface 13 toa bleed surface 11 is set to 2 μm, thereby increasing the negativepressure. By adjusting this depth, the magnitude of the negativepressure can be adjusted. Therefore, the negative pressure can be moreincreased as compared with the third embodiment, and the amount ofreduction of the flying height due to the decrease of the ambientpressure can be made smaller as compared with the third embodiment. Withthe increased negative pressure, a variation of the flying height due tothe difference of the peripheral speed of the disk can be furtherreduced. And besides, similar effects as described above for the firstembodiment can be expected.

A fifth embodiment of the present invention will be described withreference to FIG. 11. FIG. 11 is a perspective view of the fifthembodiment of a slider of the invention, showing a flying surfacethereof.

This embodiment differs from the first embodiment in that only oneflying pad, which is generally equal in size to a slider body, isprovided on a slider. A step surface 12 is provided around a flatsurface portion 13. In this embodiment, the step surface 12 is thusprovided generally over the entire periphery of the flat surface portion13, and with this construction, even when an air stream flows obliquelyinto the slider 1 (in this case, the slider is arranged at an anglerelative to the direction of the periphery of the disk), a predeterminedflying height can be obtained over the entire circumference of the disksince the step surface 12 produces a flying force. And besides, sincethe only one flying pad is provided on the slider, the compact design ofthe slider can be easily achieved. Furthermore, microscopic projections17 as described above for the first embodiment are provided at theinflow-side portion of the step surface 12, and therefore similareffects as described above for the first embodiment can be expected.

A sixth embodiment of the present invention will be described withreference to FIG. 12. FIG. 12 is a perspective view of the sixthembodiment of a slider of the invention, showing a flying surfacethereof.

This embodiment differs from the fourth embodiment in that rear stepsurfaces 18 extend rearward from opposite side surfaces of a flatsurface portion 13, respectively, and that microscopic projections 17are provided on the rear step surfaces 18, respectively. In thisembodiment, the step surface 12 is provided generally over the entireperiphery except a magnetic head-mounting surface, and with thisconstruction even when an air stream flows obliquely into the slider 1,a predetermined flying height can be obtained over the entirecircumference of the disk as in the fourth embodiment since the stepsurface 12 produces a flying force. And besides, by increasing thenumber of the microscopic projections 17, the effect of the negativepressure is enhanced, thereby achieving the slider having a more stableflying height. Furthermore, the microscopic projections 17 as describedabove for the first embodiment are provided at the inflow-side portionof the step surface 12, and therefore similar effects as described abovefor the first embodiment can be expected.

The number of the above-mentioned microscopic projections 17 is notlimited to two, and an optimum number of microscopic projections 17 canbe provided in so far as these projections do not adversely affect theflying force. The microscopic projections 17 are made of a material hardenough to withstand the contact and sliding contact between the magneticdisk 70 and the slider 1 and are formed by thin film process such asetching.

The microscopic projection 17 has a cylindrical shape, and with thisconfiguration, the length of the edge of the microscopic projection forcontact with the magnetic disk 70 is shorter as compared with the casewhere the microscopic projection has a rectangular shape. Therefore, thecontact area is reduced, so that the sticking force is reduced. Thedistal end of the microscopic projection 17 is not limited to the flatsurface, and in order to reduce the stress of contact with the magneticdisk, this distal end can be formed into a semi-spherical shape or ashape having a curvature.

The microscopic projections 17 can be easily formed by etching.

FIG. 13 shows a specific method of forming flying pads and microscopicprojections 17.

First, a first mask 21, shown in FIG. 13B, is placed on a slidersubstrate 20 shown in FIG. 13A, and the first-stage etching is effected,thereby forming flying pads. Then, a second mask 22, shown in FIG. 13C,is placed on the slider substrate 20, and the second-stage etching iseffected as shown in FIG. 13D, thereby forming step surfaces 12 andmicroscopic projections 17. As a result, there is produced the slider inwhich the height Dp of the microscopic projections 17 is equal to thedepth (height) Ds of the step surfaces 12. Namely, at this time, thereis produced the slider having the microscopic projections 17 whoseheight is equal to a flat surface portion 13.

If it is desired that the height Dp of the microscopic projections 17should be higher than the depth (height) Ds of the step surfaces 12 forthe purpose of preventing the sticking, a third mask 23, shown in FIG.13E, is placed on the slider, and the flat surface portions 13 areetched, and by doing so, this design can be obtained. In the type ofmagnetic disk device required to solve the sticking problem, such as oneusing a CSS system, the process up to the step of FIG. 13E must beperformed.

Examples of this etching process includes a chemical etching process,such as laser inducing chemical etching and plasma etching, a physicaletching process, such as reactive ion milling, and an electrochemicaletching process such as electrolytic etching. By the use of theseetching processes, the flying pads and microscopic projections ofvarious shapes can be formed. And besides, the depth of the stepsurfaces and the height of the microscopic projections can be adjusted.

In this method, although the microscopic projections 17 are made of thesame material as that of the slider substrate 20, these projections canbe formed by carbon, diamond-like carbon, or hydrogen- or nitrogen-addedcarbon, using a similar thin film process. The wear resistance of themicroscopic projections 17 can be enhanced by the use of thesematerials. Further, protective films can be formed respectively on theflat surface portions 13 and microscopic projections 17 for contact withthe disk 70, and by doing so, the wear resistance can be enhanced.Because of the enhanced wear resistance, the lifetime of the flatsurface portions 13 and microscopic projections 17 can be increased, andalso the amount of production of dust can be reduced, so that thereliability of the device is enhanced. The above protective films areformed by vapor deposition, sputtering, CVD (chemical vapor deposition)and so on.

FIG. 14 shows a magnetic disk device including a magnetic head slider ofthe present invention.

The magnetic head slider (hereinafter referred to merely as “slider”) 1is supported by a suspension 81, and the suspension 81 is connected to aguide arm 82. The guide arm 82 is pivotally moved about an axis of apivot bearing 83 by a voice coil motor 84, thereby moving the slider 1to a desired radial position on a magnetic disk 70 rotated by a spindlemotor 60. In this manner, the magnetic head slider 1 reads and writedata relative to the magnetic disk 70. These mechanisms are sealed by abase 90 and a cover (not shown).

Although the magnetic disk device of this embodiment employs a CSSsystem, the slider of the present invention can be mounted on a magneticdisk device using a load-unload system in which when the rotation of thedisk is stopped, the slider 1 is taken refuge from the disk 70.

The magnetic head slider of the present invention is effectiveparticularly for a smooth magnetic disk in which the surface roughnessof the magnetic disk surface is small. More specifically, in order toachieve a surface recording density of not less than 10 Gb/inch², it isnecessary to reduce the flying height of the slider to not more than 20nm, and in order to achieve this, it is necessary to reduce the meansurface roughness Ra of the magnetic disk to not more than 2 nm.

The mean surface roughness Ra is measured by using a surface roughnessmeter of the tracer type, and the surface is measured over a length of 1mm, and the measurement is effected at a cut-off frequency of 25 Hzwhile ignoring 0.1 mm-long opposite end portions of this length. In themeasurement using AFM (Atomic Force Microscope), the measurement iseffected over a square area (10 μm×10 μm).

In the case of a smooth disk having Ra (≦2 nm), even when the flyingslider is brought into contact with the magnetic disk surface for somereason, the friction coefficient is large, and therefore with theconventional slider, a large frictional force F is produced. When thevalue of F becomes large, the conventional slider can be easily turnedand leaned forward to damage the magnetic disk surface. On the otherhand, in the present invention, even if the mean surface roughness Ra ofthe magnetic disk is less than 2 nm (Ra<2 nm), only the microscopicprojections, formed on the slider, are brought into contact with themagnetic disk surface, and the corner portion of the slider will not bebrought into contact with the magnetic disk surface, and therefore thedisk surface will not be damaged. Therefore, there can be provided theslider having the low flying height and high reliability, and also themagnetic disk of a large capacity can be achieved.

As described above, even if the magnetic head slider of the presentinvention is brought into contact with the rotating magnetic disk forsome reason at the time of CSS or during the flying of the slider, theslider is less liable to lean forward, and even if the slider leansforward, the front edge of the step surface will not damage the magneticdisk surface. And besides, even if the ambient atmospheric pressuredecreases, the predetermined flying height can be achieved. Furthermore,using this slider in combination with the smooth disk, the magnetic diskdevice of a large capacity and high reliability can be achieved.

What is claimed is:
 1. A magnetic head slider comprising a magnetic headfor reading/writing information from/into a magnetic disk and a slideron which the magnetic head is mounted, wherein said slider has threesurface portions with levels which are different from each other on asurface facing to the magnetic disk upon read/write operation of themagnetic head slider, said three surface portions including a firstsurface portion forming a pad surface, a second surface portion having alevel which is lower than a level of the first surface portion and athird surface portion having a level which is lower than the level ofthe second surface portion, said second surface portion being providedat a side opposite to a side on which the magnetic head is mounted withrespect to said first surface portion, and said third surface portionbeing provided at the side on which the magnetic head is mounted withrespect to said first surface portion, and wherein a projection isprovided on said second surface portion.
 2. A magnetic head slideraccording to claim 1, wherein two first surface portion are provided ina width direction of the slider.
 3. A magnetic head slider according toclaim 2, wherein said second surface portion is extended to said twofirst surface portions.
 4. A magnetic head slider according to claim 1,wherein said second surface portion is extended beyond both ends of saidfirst surface portion.
 5. A magnetic head slider according to claim 1,wherein a difference in the levels of the first surface portion and thesecond surface portion is less than 300 nm.
 6. A magnetic head slideraccording to claim 1, wherein a level of said projection is higher thanthe level of the first surface portion.
 7. A magnetic head slideraccording to claim 1, wherein said projection is a cylindrical shape. 8.A magnetic head slider according to claim 1, wherein said projection hasa planar end surface.
 9. A magnetic head slider according to claim 1,wherein said projection has a curved end surface.
 10. A magnetic headslider comprising a magnetic head for reading/writing informationfrom/into a magnetic disk and a slider on which the magnetic head ismounted, wherein said slider has a plurality of flying pads on a surfacefacing to the magnetic disk upon reading/writing operation of themagnetic slider, said plurality of flying pads including two flying padsprovided at an air-inflow side of the slider and at least one flying padprovided at an air-outflow side of the slider, said flying pads eachcomprising a first flat surface portion, and a second flat surfaceportion having a level which is lower than a level of the first flatsurface portion and is provided at an air-inflow side with respect tosaid first flat surface portion, and said air-inflow side flying padseach having a projection with a level which is higher than the level ofthe first flat surface portion and provided in the vicinity of an outercorner of said second flat surface portion.
 11. A magnetic head slideraccording to claim 10, wherein said air-inflow side flying pads areoffset inwardly from opposite sides and the air-inflow side of theslider.
 12. A magnetic head slider according to claim 11, wherein rearstep surface portions having a level which is the same as the level ofsaid second flat surface portion are provided along outer sides of theslider.
 13. A magnetic head slider according to claim 12, wherein acentral step surface portion having a level which is the same as thelevel of said second flat surface portion and interconnecting saidsecond flat surface portion is provided between said air-inflow sideflying pads.
 14. A magnetic head slider according to claim 10, whereinsaid at least one flying pad provided at an air-outflow side of theslider includes one flying pad provided at a center in a widthwisedirection of the slider.
 15. A magnetic head slider according to claim10, wherein the magnetic head is provided on the flying pad provided atan air-outflow side of the slider.
 16. A magnetic head slider comprisinga magnetic head for reading/writing information from/into a magneticdisk and a slider on which the magnetic head is mounted, wherein saidslider has a plurality of flying pads on a surface facing to themagnetic disk upon reading/writing operation of the magnetic slider,said plurality of flying pads including one flying pad provided at anair-inflow side of the slider and at least one flying pad provided at anair-outflow side of the slider, said air-inflow side flying padincluding a first flat surface portion extending in the widthwisedirection of the slider, a second flat surface portion having a levelwhich is lower than a level of the first flat surface portion andprovided at an air-inflow side with respect to the first flat surfaceportion and extended along outer sides of the slider beyond the firstflat surface portion, and projections provided in the vicinity of outercorners of the second flat surface portion and extensions of the secondflat surface portion.
 17. A magnetic head slider according to claim 16,wherein the at least one flying pad provided at an air-outflow side ofthe slider includes one flying pad provided at a center in a widthwisedirection of the slider.
 18. A magnetic head slider according to claim16, wherein the magnetic head is provided on the flying pad provided atan air-outflow side of the slider.